Blank for the manufacturing of fiber-reinforced coatings or metal components

ABSTRACT

A blank material for manufacturing fiber-reinforced coatings or metal components comprising fibers made of a high-strength material and metals or metal alloys, and a process for manufacturing the blank, and for manufacturing coatings and components made therefrom. The fibers are aligned in the blank in parallel to its axis, and metal wire meshes are knitted around them, with the fibers embedded at a distance from one another. By means of high-temperature isostatic pressing, metal components can be made, through which the reinforcing fibers extend at a uniform distance.

BACKGROUND AND SUMMARY OF THE INVENTION

This invention relates to a blank for use in manufacturingfiber-reinforced coatings or metal components, comprising fibers made ofa high-strength material and metals of a lower strength than the fibers,as well as a process for manufacturing the blank, the coatings or thecomponents.

U.S. Pat. No. 3,936,550, discloses a process for manufacturingfiber-reinforced coatings or metal components comprising fibers of ahigh-strength material and titanium or titanium alloys as the metal. Forthis purpose, the fibers are isostatically pressed between two titaniumfoil layers at high-temperature. However, because the fibers are notfixed in their position between the foil layers, they may becomesuperimposed on one another or contact one another, during compressionand therefore weaken the composite material at these points.Furthermore, such fibers and foil layers are relatively stiff, andcannot be applied or formed onto components or cores beforehigh-temperature isostatic pressing. In addition, the fibers consist ofboroxides which lose their stability even at a low thermal stress, andundergo a plastic deformation.

Another disadvantage of the known blank made of titanium foil layers andboroxide fibers is that, when the blank is compressed to formfiber-reinforced metal plates, the packing density of the fibers islimited. For components having several fiber layers above one another,when the blank disclosed in U.S. Pat. No. 3,936,550 is used, a metalfoil layer is disposed between each fiber layer, which limits thepacking density of the fibers. When the packing density of the fiberswithin one fiber layer is high, there is the risk that insufficientmetal material will penetrate between the fibers during the compressionto form a fiber-reinforced metal; thus pores, holes, or cavities whichare free of matrix metal can remain in the composite material, weakeningit and posing an increased breakage risk for the fibers.

It is an object of the present invention therefore to provide a blank ofthe above-mentioned type which can be formed onto components or coreswithout shifting of the fiber position, and without forming pores orcavities. The blank according to the invention therefore yieldsfiber-reinforced metal components with a high packing density of thefibers, and permits thermal pressing processes without any damage to thefibers of the blank.

According to the invention, this object is achieved in that the fibersare aligned parallel to the long axis of the blank, are embedded in aspaced manner in knitted metal wire meshes, and are stable with respectto high temperatures.

The blank according to the invention has the advantage that it isextremely flexible mechanically and in fact has superior flexibilitycompared to woven or felt structures. It can therefore be applied in awider range of environments, and permits fiber-reinforced metalstructures which up to now could not be achieved, by pressing orcompressing of blanks according to the invention. The packing density ofthe fibers is limited only by the wire gauge of the knitted metal wiremeshes. A blank according to the invention which is compressed to form afiber-reinforced metal component, a semifinished metal product or ametal coating, has no holes, cavities or pores which are free of matrixmetal, since the metal wire meshes completely surround each fiber. Bythe use of fibers in the blank which are stable at high temperatures,thermal pressing processes may advantageously be used during furtherprocessing of the blank.

A preferred material for the fibers is silicon carbide, which not onlyallows maximum temperatures for further processing but also has anextremely high stability. In the preferred use of long silicon carbidefibers, blanks which can be wound up, and are extremely flexible andlong may also be manufactured.

To improve the further processing of the blank, as well as itscompressibility and the spacing of the fibers, the fibers are preferablylong silicon carbide fibers with a metal coating made of the same metalor of the same metal alloy as the metal wire meshes. By means of such ametal coating, the packing density of the fibers can also be increased.

In a preferred construction of the blank, the metal wire meshes arelinked by means of their tuck loops in a cross-sectionally triangularmanner. This has the advantage that, in the center of gravity of thesurface of each triangular link, a fiber may be arranged as the woofyarn. Because each triangular link is linked at its corners with anadjacent mesh or an adjacent tuck loop, the blanks can be advantageouslydeformed and can be adapted to a component or formed body, without anycontact between or falling apart of, or shifting of the fibers or thecoated fibers. Thus, the advantageous draping capacity of a knittedstructure can be utilized to the manufacture fiber-reinforced metalliccomponents.

A high packing density is achieved in a preferred embodiment of theblank in which the metal wire meshes supplement one another to form auniformly thick blank of metal wire meshes that are triangularly linkedto be standing on a vertex and a side. In this case, a lower metal wireforms the metal wire meshes which cross-sectionally stand on the sidethroughout a blank, and an upper metal wire forms the upper meshes whichstand on the vertex, while the pertaining tuck loops alternately form alink between the upper and the lower metal wire. Therefore, very thinmats are advantageously manufactured as blanks, in which case the twofiber layers are arranged offset with respect to one another.

While the fibers are of an arbitrary length, the metal wire meshes areknitted of continuous metal wires in a preferred embodiment of theinvention. This has the advantage that the blanks can be manufactured atreasonable cost on conventional industrial-scale knitting machines in amanner well known to those skilled in the art.

To further increase packing density, the fibers preferably form woofyarns placed in meshes, with the fibers which are surrounded by thelower metal wire meshes forming a lower layer, and the fibers which areembedded as the woof yarn into the upper metal wire meshes forming theupper layer. Higher packing density is achieved by means of the offsetarrangement of the fibers between the upper and lower fiber layers.

In thick blanks, the fibers are staggered in more than two layers in theknitted material of meshes, with or without a tuck loop. In this manner,advantageously arbitrary thicknesses of the blanks can be achieved.

A preferred metal for the metal wire meshes is titanium. Titaniumcomponents are particularly light weight, and are commonly used in theconstruction of engines, which are subjected to high temperatures,aggressive gas flows and high tensile stress. Fiber reinforcement, forexample, in the tensile direction, improves these characteristics andpermits a high stressing of the components and a higher reliability ofthe power units.

In the manufacture of a blank, the fibers are preferably guided as woofyarns in a knitting machine in parallel to the longitudinal axis of theblank, and metal wire meshes are knitted around them in a conventionalmanner. For this purpose, the fibers are advantageously wound in theform of long fibers off supply spools and are guided to the knittingmachine while, transversely to the woof direction, a thin metal wire isknitted around them in a close-meshed manner.

A preferred use of the blank according to the invention is for themanufacture of fiber-reinforced titanium plates, titanium rings orhalf-finished titanium products. A blank made of fibers and titaniumwire meshes placed individually or in several layers or wound into aring, is compressed by means of high-temperature isostatic pressing toform fiber-reinforced titanium plates, titanium rings or semi-finishedtitanium products. The plates, rings or semi-finished products aredistinguished by the regular distribution of the fibers in a metalmatrix made of titanium.

Another preferred use of the blank is for the manufacture of aself-supporting component made of fiber-reinforced titanium. For thispurpose, one or more layers of a blank made of fibers and titanium wiremeshes are pulled onto a core and compressed by means ofhigh-temperature isostatic pressing; then the core is removed. In thecase of an open structure this may be achieved simply by withdrawing thecore as a single unit. For partially closed components, the core iseither made to be divisible or is removed, for example, by burning-outor etching-out. The use of the blank according to the invention in thisprocess has the advantage that the direction of the fibers in anyposition can be adapted to the constructional requirements, and evenwhen fiber layers cross one another, contact between the fibers or asliding of the fibers on one another is prevented. Furthermore, engineblade devices in the blade area may be manufactured from this material,advantageously permitting a high tensile load in the direction of theblade axis.

In addition, the blank may advantageously be used to manufactureself-supporting ring-shaped components, such as shrouds for turbineblade wheels with sealing tips and disk-shaped flanges. For suchapplications, a ring-shaped component is first wound from a blank bymeans of meshes consisting of titanium or of a blade material, andsubsequently the sealing tips and disk-shaped flanges withtitanium-coated or blade-material-coated long SiC fibers are wound ontoor on the ring-shaped blank on negative forms. The long fibers and theblank are isostatically compressed at a high temperature to form acomponent. Because of the increased tensile loading capacity of theseshrouds, it is possible for the first time to equip moving blade wheelswith a co-rotating dynamically and thermally stable and closed shroud,and to aerodynamically seal the wheels by way of sealing tips arrangedradially on the outside so that a further increase of the efficiency ofgas turbine engines is achieved.

The blank according to the invention can also be used in coatingprocesses. In this case, the blank is placed, wound, glued, soldered,diffusion-welded or spot-welded in one or several layers onto thecomponent, and by means of a high-temperature isostatic pressing on thecomponent is compressed to form a fiber-reinforced coating.

This coating process has the advantage that highly stressed components,such as engine shafts made of light metals, can be reinforced by meansof a stability-increasing coating. Furthermore, in the blade area, theengine blade devices may be constructed to be thinner and thereforelighter.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is a partially schematic cross-sectional view of a two-layerblank;

FIG. 1b is a top view of a two-layer blank;

FIG. 2 is a view of a fiber-reinforced titanium plate formed by hightemperature isostatic compression of a multi-layer blank according tothe invention;

FIG. 3 is a view of a blank which has been wound onto a tube;

FIG. 4 is a view of a blank wound onto a tube after the compressing toform a tube coating as a fiber-reinforced engine shaft;

FIG. 5 is a view of a blade wheel comprising a shroud consisting of theblank and coated long fibers;

FIG. 6 is a cross-sectional view of a shroud according to FIG. 5;

FIG. 7 is a view of the winding of a blank and metal-coated long fibersonto a shroud form;

FIG. 8 is a cross-sectional view of the wound-up shroud form beforehot-temperature isostatic pressing.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1a is a partially schematic cross-sectional view of a two-layerblank 1 with fibers 2 arranged in parallel to its longitudinal axis andwhich are embedded in metal wire meshes 3. (For simplicity, a detailedrepresentation of the weave of the metal wire meshes, shown in FIG. 1b,has been omitted from FIG. 1a, other than at the cross section.)Together with the fibers 2, the metal wire meshes 3 form a mat which isbendable and flexible. Blanks 1 of this type may be placed on oneanother, and the direction of the fibers 2 may be adapted to theconstructional requirements. High temperature isostatic compression ofsuch a blank produces a fiber-reinforced metal strip which has a highpacking density of the fibers 2, with each fiber 2 completely encased bymetal. The fibers 2 have a thickness of from 20 to 150 μm, while thediameter of the metal wire is from 20 to 80 μm.

An upper layer 25 of the fibers 2 is surrounded by upper metal wiremeshes 26, with the tuck loop 27 of the lower metal wire meshes 28 andthe tuck loop 31 of the upper metal wire meshes 26 linking the upper andthe lower metal wire meshes 26, 28 with one another. By means of thetriangular linking, the upper layer 25 of the fibers 2 is arranged in anoffset manner with respect to a lower layer 29 of the fibers 2. Thefibers 2 in the lower fiber layer 29 are enclosed by the lower metalwire meshes 28 and by tuck loops 31 of the upper metal wire meshes 26,each metal wire mesh being linked with the adjacent mesh in a triangularmanner. This knitted structure is distinguished by its high drapingcapacity and flexibility.

FIG. 1b is a top view of a two-layer blank 1. The alignment of thefibers in parallel to the longitudinal of the blank axis isdemonstrated, with the knitting surrounding all sides of the upper layer25 of the fibers 2 and of the lower layer 29 of the fibers. It is onlyfor a better differentiation that the metal meshes 3, 26 and 28 areshown far apart. For the blank 1 throughout which the fibers extend, themetal wire meshes 3, 26 and 28 are knitted extremely closely so thateach fiber is completely enclosed by metal wire and high-temperatureisostatic compression of the blank results in a metal matrix withoutpores.

FIG. 2 illustrates a multi-layer blank which has been compressedisostatically at a high temperature to form a fiber-reinforced titaniumplate 4. In this example, only two blanks were placed in layers andcompressed with one another, so that the fibers 2 are made of siliconcarbide and remain equidirectional. As a result of high-temperatureisostatic compression, the fibers 2 made of silicon carbide arecompletely and uniformly surrounded by a titanium matrix 5.

FIG. 3 illustrates a blank 1 which is wound onto a tube in a doublelayer, with the winding direction arranged angularly with respect to thetube axis, and the first layer 9 being wound at a different angle thanthe second layer 6. Such wound blanks 1 may be processed to form aself-supporting component, if, after the high-temperature isostaticpressing, the tube is withdrawn or etched out.

FIG. 4 shows a blank wound onto a tube 7 and compressed by means ofhigh-temperature isostatic pressure to form a tube coating 8 for afiber-reinforced engine shaft. The high-strength fiber-reinforcedcoating 8 of the tube 7 (which in this example consists of aluminum)provides an extremely light torsion-proof engine shaft.

FIG. 5 shows a blade wheel comprising a shroud 11 consisting of theblank and additional long fibers coated with titanium which encloses theblades 12 in a ring-shaped manner radially on the outside. The sealinggap 13 between the turbine housing 14 and the blade wheel 10, whichcomprises the blade disk 22, the blade ring 23 with the blades 12 andthe shroud 11, is minimized by way of very effective sealing tips 15which are integrally arranged on the shroud 11. The sealing tips 15 arebest shown in FIG. 6 which is a cross-sectional view of a shroud 11according to FIG. 5. The shroud 11 consists essentially of a shroud ring16, two disk-shaped flanges 17 and 18 on the outer surfaces of the ringand the sealing tips 15. The inside radius of the shroud ring 16increases from flange 17 to flange 18.

In order to manufacture such a component from fiber-reinforced titanium,the blank 1 according to the invention, for the shroud ring 16, is woundin several layers on a form 19 in the direction of the arrow A asillustrated in FIG. 7. As shown in FIG. 8, the flanges 17 and 18 and thesealing tips 15 may be wound onto the form 19 by means oftitanium-coated long SiC fibers. The free surfaces of the blank 1 andthe titanium-coated long SiC-fibers 20 are encapsulated after thewinding and evacuated. The whole construction with the form 19 and withthe wound unfinished component 21 and the encapsulation (not shown) arethen pressed isostatically at a high temperature. After the pressingoperation, the form 19, which can be divided in a multiple manner, isseparated from the component consisting of the fiber-reinforced metal,and the self-supporting component is freed of its encapsulation andcorresponding to FIG. 5 is mounted on the blades 12. Subsequently, theblade ring 23 with the shroud 11 is placed on the blade wheel disk 22.

Although the invention has been described and illustrated in detail, itis to be clearly understood that the same is by way of illustration andexample, and is not to be taken by way of limitation. The spirit andscope of the present invention are to be limited only by the terms ofthe appended claims.

We claim:
 1. A blank material for manufacturing fiber reinforcedcoatings and metal components comprising:a plurality of fibers made froma material which has a high tensile strength and is stable at hightemperatures, wherein the material is SiC; a knitted metal wire materialcomprising a plurality of metal wire meshes made of titanium, the metalwire material including lower metal wire meshes and upper metal wiremeshes; said fibers being knitted into and held in said wire material inan orientation in which said fibers are separated from each other andare parallel to each other and to an axis of said blank; wherein thefibers are woof yarns and are arranged in an upper layer and in a lowerlayer, the lower layer being surrounded by the lower metal wire meshes,and the upper layer being surrounded by the upper metal wire meshes, andthe fibers extend in straight lines.
 2. A blank according to claim 1,wherein the fibers are long silicon carbide fibers.
 3. A blank accordingto claim 1, wherein the fibers are long silicon carbide fibers having ametal coating made of the same material as the metal wires meshes.
 4. Ablank according to claim 1, wherein said metal wire meshes are crosssectionally triangular, and are linked together by tuck loops.
 5. Ablank according to claim 3, wherein said metal wire meshes are crosssectionally triangular, and are linked together by tuck loops.
 6. Ablank according to claim 4, wherein said knitted metal wire materialcomprises upper metal wire meshes and lower metal wire meshes, saidupper meshes and said lower meshes complementing each other to form auniform thickness of metal wire meshes.
 7. A blank according to claim 6,wherein said upper and lower meshes have triangular cross section, withsaid upper meshes oriented with a vertex of said triangular crosssection directed downwardly and said lower meshes oriented with a vertexof said triangular cross section directed upwardly, and wherein suchloops alternately link said upper and lower meshes.
 8. A blank accordingto claim 1, wherein the metal wire meshes are knitted from a continuousmetal wire.
 9. A blank according to claim 4, wherein the metal wiremeshes are knitted from a continuous metal wire.
 10. A blank accordingto claim 7, wherein the metal wire meshes are knitted from a continuousmetal wire.
 11. A blank according to claim 7, wherein the fibers arewoof yarns and are arranged in an upper layer and in a lower layer, thelower layer being surrounded by the lower metal wire meshes, and theupper layer being surrounded by the upper metal wire meshes.
 12. A blankaccording to claim 1, wherein the fibers are fixed in the knittedmaterial in a staggered fashion in more than two layers.
 13. A blankmaterial for manufacturing fiber reinforced coatings and metalcomponents comprising:a plurality of fibers made from a material whichhas a high tensile strength and is stable at high temperatures, whereinthe material is SiC; a knitted metal wire material comprising aplurality of metal wire meshes made of titanium, the metal wire materialincluding lower metal wire meshes and upper metal wire meshes; saidfibers being knitted into and held in loops formed by said wire materialin an orientation in which said fibers are separated from each other andare parallel to each other and to an axis of said blank, wherein eachloop of said wire material engages at least one of said fibers; whereinthe fibers are woof yarns and are arranged in an upper layer and in alower layer, the lower layer being surrounded by the lower metal wiremeshes, and the upper layer being surrounded by the upper metal wiremeshes, and the fibers extend in straight lines.